Sara O'Neill is the daughter of Mike.[1] She has been married to Jack O'Neill and they had a son, Charlie. They were living in a house located in Winter Park. They were happy together, but one day in 1995, Charlie accidentaly killed himself with O'Neill's personal gun. O'Neill withdrawed into himself, breaking up the marriage. According to O'Neill, she forgave for what happenend, but she couldn't forget. Part of her has never been able to get over her former husband. Sara still believes the two had the greatest relationship, despite the tragedy that would eventually end their marriage. (Stargate, SG1: "Children of the Gods", "Cold Lazarus").

Sara O'Neill is working on her father's car, when she's aborded by an alien who looks like Jack O'Neill. He claims he wants to see Charlie, but she's scared because of his reaction and runs to the house. Then, Mike, her father, comes out and warns "O'Neill". He then invites him in the house and brings him to Charlie's bedroom. As "O'Neill" gets downstairs, Sara says she's surprised to see him like this as they never talk about Charlie since he died.

Later in a park, "O'Neill" tries to understand what's going on with Sara, and then she tells him that she knows how he filled because of Charlie's death, but he has to remove this armor he puts on since. "O'Neill" asks her to let him bring back Charlie to the Stargate. Sara says that Charlie is gone but suddenly, "O'Neill" collapses by the effects of blue bolts of energy. Horrified, Sara brings him to the hospital.

At the hospital, "O'Neill" remembers they brought Charlie here after the accident. Then he starts emetting energy and burns Sara's hands. A nurse is widding bandage on her hands, but she runs as she sees other blue lightning. Colonel Jack O'Neill then arrives, much to Sara's surprise. They hug and O'Neill insists if she's all right and asks where is the fake O'Neill. He leaves her and Captain Carter takes care of Sara.

Later O'Neill comes back to Sara with the Unity who has shifted to a copy of Charlie. Sara is shocked, but O'Neill says it's not Charlie and he has to bring him to the Stargate. When he leaves her, she whispers: "Take care of yourself, Jack."

As O'Neill is rapidely aging because of nanites, he takes a notebook and a pen, and starts to write "Dear Sara", but nothing else. After a moment, he closes the notebook and throws the pen to the floor.

O'Neill is badly wounded and stranded with Captain Carter inside an icy cavern. As they are freezing to death, Carter lies on O'Neill's side and tries to warm him up. O'Neill just whispers the name of Sara.